1. Field of the Invention
The invention relates to a road condition detecting system that obtains information about road conditions via vehicle-to-vehicle communications.
2. Description of the Related Art
Various systems for preventing collisions or alleviating or absorbing shock at the time of collisions have been developed. It is important for this type of system to detect obstacles, such as other vehicles or pedestrians, which exist in the vicinity of the own vehicle. To this end, the vehicle is installed with a camera or a radar sensor, and is arranged to detect obstacles by using image information or radar information. However, the own vehicle's ability to detect obstacles is limited by one or more factors, such as the range of detection of the sensor or a blind spot that cannot be seen from the own vehicle. Thus, some vehicles in the system utilize vehicle-to-vehicle communications, or the like, so as to obtain information about obstacles from other vehicles and so forth. For example, a system as disclosed in Japanese Patent Application Publication No. 2005-207943 obtains information on the position of another vehicle via vehicle-to-vehicle communications, and, if it is determined from map data and the information on the position of the vehicle (other than the own vehicle) that there is a structure or object that puts the vehicle out of view, the system provide a translucent or transparent image of the structure that puts the vehicle out of view on a three-dimensional map so as to allow the vehicle to be recognized.
However, not all the vehicles are installed with communication devices for conducting vehicle-to-vehicle communications, and pedestrians, and the like, do not carry such communication devices. Therefore, the above-described system obtains only the information on the positions of other vehicles equipped with such communication devices, and is not able to obtain information on the positions of pedestrians or other vehicles (e.g., vehicles that are not equipped with communication devices). Also, since the system receives position information from all of the other vehicles equipped with the communication devices and located in the vicinity of the own vehicle, a large communication band may be required at intersections, or the like, having a large amount of traffic, or unnecessary information may be obtained from other vehicles having no chance of resulting in considerably inefficient communications.